This invention relates generally to apparatus used for cutting vegetation, and more particularly relates to a lawnmower of the type in which the cutting elements are mounted for rotation about a neary vertical axis within the mower housing. The present invention is a lawnmower which utilizes cutting of grass achieved by contact between the grass and free lengths of highly flexible filament mounted for rotation about a nearly vertical axis.
Trimming and edging utilizing a trimmer which uses a filament spun at high speed about an axis is known. Such a concept is generally disclosed in U.S. Pat. No. 3,693,225 to Langenstein. Further, U.S. Pat. No. 3,664,102 to Reber teaches a cutter mechanism of more general application to cutting vegetation in agriculture and lawn mowing applications in which nylon filaments are disclosed as cutting elements. In various of the embodiments shown in the Reber patent, multiple filaments mounted on a single cutting head is shown.
It is also known to provide rotary cutting elements in which the cutting elements are somewhat more flexible than the traditional relatively rigid steel blades, either by providing metal blades with a resilient connection to a central member or, in the case of a recently introduced lawnmower, sometimes referred to as a Roper "Whip-Stick" mower, cutting elements which are relatively short replaceable plastic pegs of a generally conical section which purportedly have significantly more give and flexibility than conventional rigid mounted steel bladed configurations.
Distinctly different problems from those addressed by trimming and edging devices are addressed in a residential or other ornamental lawn cover cutting applications. While the trimming and many general vegetation cutting applications do not require precise control and even height-of-cut, this is not true in residential and ornamental lawn cover applications. Also, trimming and edging operations do not involve cutting large amounts of vegetation, and trimmers and edgers therefore do not face the problem of disposing of cut vegetation. In residential lawn mowing usage, the user's demand that the machine have an ability to both cut the grass at a finely controlled height-of-cut and provide means for collecting or disposing of the cut grass particles must be met.
In addition, by comparison to the trimmer and edger applications in which filament cutters have typically been used, the lawn mowing application represents a very signficant increase in instantaneous vegetation load to be cut during normal operation. In a trimmer and edger, the load is easily controlled by the user merely by the rate at which the trimmer is moved through the vegetation to be trimmed or edged. In the lawnmowing application, slowing down or making repetitive passes over a single portion of a lawn would be highly objectionable from a consumer standpoint.
By comparison to the traditional fixed rigid blade machines, the advantages of a lawnmower capable of operating with highly flexible filament type cutting elements are significant. First, because of the resiliency of the cutting elements, they can strike solid objects on the lawn surface without significant damage to the mower drive structure, as the cutting element will readily flex. Second, in embodiments where means are provided for metering out replenishing lengths of filament, the mower does not require sharpening or blade maintenance. Yet, to the best of applicant's present knowledge, there is presently no commercially available mower for residential and other ornamental lawn covers utilizing highly flexible filament type cutting elements.
Applicant has developed a mower suitable for lawn cutting applications which utilizes highly flexible filament type cutting elements of a replenishable nature, and yet provides a system in which agitation of uncut grass and orderly evacuation of a mower housing can be achieved. In addition, with applicant's invention, cutting at a height sufficiently controlled to result in acceptable ornamental lawn cover appearance without a noticeable scalloping effect caused by successive cuts and without an unacceptable number of risers, that is, uncut grass filaments, is achieved.